Diamondback Energy will buy rival Endeavor Energy Resources in a cash-and-stock deal valued at about $26 billion to create a drilling giant in the Southwest United States. The transaction includes approximately 117.3 million shares of Diamondback common stock and $8 billion in cash. Existing Diamondback shareholders are expected to own about 60.5% of the combined company, while Endeavor’s equity holders are anticipated to own approximately 39.5%.